This invention relates generally to a fluid mixer assembly and more particularly to a shielded conduit for mixing exhaust gas from an exhaust gas recirculation (EGR) system with the intake air supply of an internal combustion engine.
An Exhaust Gas Recirculation (EGR) system reduces unwanted emissions resulting from the combustion process in an internal combustion engine. When combustion occurs in an environment with an excess of oxygen, peak temperatures in a combustion chamber increases leading to the formation of NOx. The EGR system introduces exhaust gas having a low oxygen concentration into an inlet manifold of the internal combustion engine to lower the concentration of oxygen. By reducing the oxygen concentration, fuel burns slower and reduces peak temperatures in the combustion chamber. Also, the recirculated exhaust gas absorbs some of the heat released during combustion.
One problem inherent with the introduction of exhaust gas into the inlet manifold, is that during operation, engines typically exhibit different firing characteristics for each combustion chamber. It has been found that the overall charge introduced to the cylinder""s inlet valves lacks uniformity and can vary widely in quality when exhaust gas is mixed with the intake air.
Because of the desire to control the combustion event in any cylinder, and thereby to a degree to control the quality of the overall charge introduced, it has made it desirable to more closely regulate the composition of the overall charge. That is, the intake air and the exhaust gas are combined to form an aggregate charge. To have the engine operate efficiently and satisfactory from the point of view of emissions control, it is desirable to maintain a degree of uniformity and consistency in the initial aggregate charge and thus control the mixing between constituents.
The present invention is directed to overcoming one or more of the problems set forth above.
In one aspect of the present invention a fluid mixer assembly comprises an inlet conduit and a shielded conduit. The inlet conduit has a connector bore that is formed by a cylindrical surface and has a longitudinal axis. The connector bore forms a first cavity which has a preestablished volume. The inlet conduit has a first fluid passing therethrough. The shielded conduit is partially positioned within the first cavity and has a first surface extending between a pair of ends and defines a first predetermined width. A second surface extends between a pair of ends and defines a second predetermined width. A pair of third surface connects a corresponding end of the first and second surfaces. The pair of third surfaces are at an acute angle with said longitudinal axis. The second predetermined width is greater in length than the first predetermined width. A perimeter at the first surface, the second surface, and the pair of third surfaces define a second cavity. The shielded conduit has a second fluid passing therethrough and is in communication with the first fluid.
In another aspect of the present invention a method of mixing exhaust gas with intake air has an exhaust manifold, a shielded conduit, and an intake conduit. The method comprises the steps of passing inlet air through the inlet conduit. Passing exhaust gas from the exhaust manifold through the shielded conduit, and into the inlet conduit. Diverting the intake air about the shielded conduit into a first fluid stream and a second fluid stream. Re-combining the first fluid stream and the second fluid stream at a point downstream of the shielded conduit with the exhaust gas.